J. J. Thomson

Denae and Rebecca
Chemistry 11
Early Life

Born:
December 18, 1856
Cheetham Hill, Manchester, England
Family:
Mother – Emma Swindells
Father – Joseph James Thomson (ran an antiquarian bookshop)
Brother – Frederick Vernon Thomson (two years younger)
Education:
He went to small private schools where he demonstrated great talent and an interest in
science. At only 14 years of age, he was admitted to Owens College in 1870. His parents
planned to enroll him as an apprentice engineer to Sharp-Stewart & Co., but these plans
changed when his father died in 1873.
Later Life

Education:
In 1876, he moved to Trinity College, Cambridge. In 1880, he got his BA in mathematics
(Second Wrangler and 2nd Smith's prize) and MA (with Adams Prize) in 1883. In 1884 he
became Cavendish Professor of Physics. One of his students was Ernest Rutherford.
Family:
Wife – Rose Elisabeth Paget
Son – George Paget Thomson
Daughter – Joan Paget Thomson
Died:
August 30, 1940
He was buried in Westminster Abbey, close to Sir Isaac Newton.
Idea of the Atom

 discovered the electron and then created the first
model of an atom with the electrons (plum pudding)
 formed the idea that in a positively charged sphere
there was negative electrons that moved/rotated
 model was later proven wrong by his student, Ernest
Rutherford
 believed that the more energy added, the more the
electrons velocity increase, if there was enough
energy, they could leave their atoms
First Experiment

First, he built a cathode ray tube with a metal
cylinder on the end. It had two slits in it, leading to
electrometers, which could measure small electric
charges. He found that by applying a magnetic field
across the tube, there was no activity recorded by the
electrometers and so the charge had been bent away by
the magnet. Therefore, proving that the negative
charge and the ray were inseparable and intertwined.
Second Experiment

Next, he proved that atoms were negatively charged. He did so by modifying
the cathode ray tube, originally built by William Crookes, by exposing the cathode ray
to an electric field and a magnetic field. The beam deflected toward the positive plate,
which meant that there must have been mysterious particles with a negative charge.
Third Experiment

Then, he figured out that there is a ratio
between the mass of the particles and the deflection.
He then proved that the negative charged particles
where smaller then an hydrogen ions, which was
believed to be the smallest atom.
Soon after, Thomson used a further-modified
cathode ray to show that there were also positively
charged particles called protons.
Contributions

Discoveries:
 The electron
 A model of the atom
 Many isotopes
 Hydrogen has only one electron per atom
 A method for separating different atoms and molecules
by using positive rays
Other:
 Determined that cathode rays were beams of electrons
 Determined the mass-to-charge ratio of an electron
 Proposed the "plum-pudding" model of the atom
 Argued that the number of electrons in an atom was approximately equal to the
atomic weight of that element
 Worked on the conduction of electricity in gases
One of Thomson's greatest contributions to science was in his role as a highly gifted
teacher. Seven of his research assistants and his son won Nobel Prizes in physics.
Accomplishments

1884: Elected a fellow of the Royal Society
1894: Royal Medal
1902: Hughes Medal
1906: Nobel Prize for Physics in recognition of the great merits
of his theoretical and experimental investigations on the
conduction of electricity by gases."
1908: Knighted
1910: Elliott Cresson Medal
1912: Appointed to the Order of Merit
1914: Copley Medal
1914: Gave the Romanes Lecture in Oxford on “The atomic theory”
1915-1920: President of the Royal Society
1918: Became Master of Trinity College, Cambridge
1922: Franklin Medal
1937: His son won the Nobel Prize for proving the wavelike properties of electrons
1991: The “thomson” (symbol: Th) was proposed as a unit to measure mass-to-charge
ratio in mass spectrometry
Bibliography

Pictures:
 http://2.bp.blogspot.com/ALZsMzupHPE/Tbx_I5tU5EI/AAAAAAAAABg/2EHNgL9e2h0/s1600/Nobel_me
dal.jpg
 http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/J.J_Thomson.jpg
/200px-J.J_Thomson.jpg
 http://cdn.dipity.com/uploads/events/30e9aae2fa011b24e974ab13eb3c11f7_1M.pn
g
 http://web.visionlearning.com/events/images/JJThomson_child.jpg
 http://electrapk.com/wp-content/uploads/2011/07/hydrogenatom.jpg
Information:
 http://en.wikipedia.org/wiki/J._J._Thomson
 http://www.nobelprize.org/nobel_prizes/physics/laureates/1906/thomsonbio.html
 http://www.aip.org/history/electron/jj1897.htm
 http://www.experiment-resources.com/cathode-ray.html